1. Field of the Invention
The present invention relates to a design data generating method and a design data generating apparatus, and more particularly to a design data generating method and a design data generating apparatus for changing an existing article shape to generate new design data for an article.
2. Description of Related Art
A new article may be designed by transforming existing article data using a CAD (Computer-Aided Design) apparatus. For example, according to one method which is used, for an article having a shape as shown in FIG. 47A, a line segment which is to be a new edge line of the article is input, and the original cross sectional shape is arranged along the new edge line while maintaining its shape, thereby generating a new shape shown in FIG. 47B.
Further, with respect to LSI layout pattern design, there has been a method in which a function cell for realizing a function unit of the designed layout pattern is replaced, thereby achieving efficient re-designing. (For example, see Japanese Patent Laid-Open Publication No. Hei 9-36238). According to another method, a cross sectional shape is extracted from an existing three-dimensional article shape, and a shape model which is classified according to the shape pattern is subjected to basic operations such as extrusion, sweep, rotation, cutting, mirror copy, etc., thereby generating a three-dimensional shape of a new article. (See Japanese Patent Laid-Open Publication No. Hei 11-45352, for example.)
Even in the case of transforming the whole article design based on the data of an existing article, rather than partial replacement of an existing article, it is sometimes desired to transform a portion of the article while another portion is maintained. In such a case, according to the conventional process, only a portion of the article which needs transformation is extracted and transformed, and then the transformed portion is once again connected to the portion which maintains the original shape. The above conventional process, however, suffers from problems that it is difficult to recognize and confirm the whole article design during transformation and that the boundary between connected portions becomes discontinuous.
There are also cases where a new article shape is desired which cannot be configured with the cross sectional shape of the existing article being maintained. In this case, it is necessary to first transform individual cross sectional shapes and then rearrange the transformed cross sectional shapes in order to obtain a new three-dimensional shape.
However, it is difficult to generate a new three-dimensional shape which the operator expects by transforming the individual cross sectional shapes, and therefore this has largely been a process of trial and error.
In addition, because there is no way of specifying how cross sectional model shapes are arranged in a new three-dimensional shape so as to satisfy the operator's desire, efficient use has not been made of an existing three-dimensional shape.